Cathode ray tube



May 17, 1960 xR. c. PALMER 2,937,233

cA'rHoDE lRAY TUBE Filed April 4, 1958 u lllmuum: l

'huub numb INVENTOR. RICHARD C. PALMER ATTORNEYS ,suited for recording sequential presentations.

ltight-seal between the glass and the metal wires.

United States Patent C) CATHODE RAY TUBE `Richard C. Palmer, Pompton Plains, NJ., assignor to (Allen B. Du Mont Laboratories, Inc., Clifton, NJ., `a'corpuration of Delaware Application April 4, 1958, Serial No. 726,579

8 Claims. (Cl. 178-6.6)

Thisinventxon relates to a cathode ray tube, and more particularly to such a tube having apparatus associated therewith which makes possible instantaneous recording .of the light pattern on the tube.

method involves theprocesses of photographic development and printing, an opticalsystem capable of photographing an'object at close range, and is not particularly Another method is'to' use xerography which requires the production of `electrostatic charge patterns, dusting, developing, etc. A third method is the use of a special potentialsensitive material which changes color when exposed to 'an electric current. `In this connection, it has been suggestedthat the faceplate of a cathode ray tube have incorporated therethrough a myriad of -wires positioned with their ends extending beyond each surface. Under this'system voltages produced by the electron beam are transmitted to the outside of the tube by selected wires to apply'a potential across the thickness of the material, thus causing itl to break down and change color to prokduce a permanent record. This particular arrangement,

:besides requiring a complicated faceplate structure, introduces the ever present problem of achieving a vacuum In addition, the presence of the wires prevents the cathode ray ytube from being used for visual examination.

Another problem in recording the pattern on the cathoderay tube faceplate arises from the fact that the glass Afaceplate must have an appreciable thickness to withstand the atmospheric pressure. course produced on a uorescent screen which is posi- 'tioned on the inner surface of the faceplate. fromthe lpattern therefore tends to disperse as it passes The light pattern is of The light through-the faceplate, thus degrading the presentation.

'It'is therefore one object of my invention to provide an improvedapparatus formaking recordings of the presentation produced by a cathode ray tube.

VIt is-another object ofV my invention to provide a cathode ray tube having a structure which provides an improved presentation.

Themode offattaining these and other objects will be apparent Ywhen the following specification is considered in conjunction with the appended drawings, of which,

.-Fig..1.is aschematic cross sectional View of the device ofimy invention; and

Fig. 2 is a perspective view ofthe structure of my novel cathode ray tube faceplate.

My invention uses a potential sensitive material which changes its local physical appearance when a sufficiently .high {electr-ical .potential causes an electrical current to 410W therethrough. Variousrecording'materials of this -sortfare known, one in particular being a paper identified as Teledeltosf This material, its characteristics, and use, are more fully described in AIEE technical paper 48- 74 entitled Western Union Teletape Facsimile by Leon G. Pollard. Basically, by invention impresses a potential across this paper when light from a cathode ray tube fluorescent screen strikes a layer of photoconductive material, reduces the resistance thereof, and thus permits a high voltage to be applied across the thickness of the special paper.

Referring now to Fig. l, there is illustrated a standard cathode ray tube 10 having the usual gun structure 12 for producing an electron beam 13, a deection system 14 (shown as an electromagnetic coil), a faceplate 16, 4and a fluorescent screen 18 on the inner surface thereof.

In accordance with my invention, the outer surface of faceplate 18 is coated with a iilm 20 of transparent conductive material, oneform of which is known as Nesa. A coating 22 of photoconductive material is positioned so thatlight from the presentation falls upon it. If desired, a lens system maybe utilized, but preferably coating 22 is placed in area contiguous relationship with film 20. As is well known in the art, photoconductive materials (such as cadmium sulfide) have a high plate 24 which positions a sheet of potential sensitive Amaterial 26 between photoconductive coating 22 and backing plate 24.

A suitable potentialis now applied between backing plate 24 and conductive film 20. 'f This potential is thus impressed across a series circuit consisting of conductive lrn 20, photoconductive coating 22, potential sensitive material 26, and conductive backing plate 24. Of this series circuit, the photoconductive coating 20 is the only one whose resistance maybe changed, and its value varies with illumination.

`My invention operates as follows. When suitable energizing signals are applied to the tube, it operates in a well known manner to produce on its fluorescent screen 18a pattern of light which is representative of the input signals. Assume for simplicity that the light pattern is a waveform. The light from this pattern traverses glass `faceplate 16 and transparent cpnductive film 20 to impinge upon photoconductive material 22. Since material 22 changes its resistance in accordance with the light impinging thereon, each elemental area thereof will attain a resistance corresponding to the illumination on said elemental area.

As the resistance of photoconductive coating 22 is changed by the light striking it, the potential established between backing plate 24 and conductive film 20 will cause a corresponding electric iield to be produced across the thickness of recording material 26, the strength of this electrostatic iield varying from area to area in accordance with the resistance pattern of photoconductive material 22 which is in turn controlled by the fluorescent presentation on screen 18. Potential sensitive material 26, reacts to the presence of the potential across its thickness by breaking down and permitting a flow of electricity. The resultant current causes the material to change its physical characteristics, color, etc. Depend- .ing upon the material used, it may inherently produce a separate pictures are produced, each of which corresponds to sequential presentations of the cathode ray tube.

An alternative arrangement is to utilize a cathode ray tube wherein the beam is deflected only horizontally. In this embodiment, recordingmaterial 26 would be in the form of a tape which moved continuously and smoothly across the face of the cathode ray tube.

It is apparent that `backing plate 24' and suitable guide rails for material 26 may be designed to either be a separate structure which can be physically removed from cathode ray tube 10, or else provide an unobstructed view when material 26 is removed. If, now, photoconductive coating 22 were to be made transparent, cathode ray tube may also be used for visual presentations.

As previously stated, the thickness of the faceplate causes an actual physical separation between fluorescent screen 18 and recording material 26, this separation producing a certain amount of fuzziness in the recorded image due to dispersion of the light. This deleterious result may -be visualized by considering a spot of light generated at a point in uorescent screen 18. The light is directed outwards through the faceplate in many directions, and is therefore known 'as divergent If now the illuminated spot is moved -a short distance, light from the second spot will also diverge, and some of it will strike or overlap the same area on which light from the first spot previously impinged. Since the intensity of the two light spots is generally different, this overlapping effect produces fuzziness. Y

Many devices have been suggested for collimating the light, that is, causing the light to come out as parallel rays so that overlap is eliminated. One of the b asic suggestions is to have the light producing spot occur at theA focal point of a lens. This solution utilizing a single lens for a cathode ray tube is obviously impractical due to the size of the lens required, and the fact that the light producing spot is constantly moving and therefore leaving the `focal point of the lens. Other suggestions have been to kuse a plurality of small lenses known as lenticules. This composite structure has the same disadvantage, namely that the light is not generated at the focal point of each lenticule and the additional problem that the light from each point passes through and is refracted by all of the other lenticules, as well as the one having its focal point at the point Where the light is generated. Another suggestion for producing collimated light has been to use a multiplicity of parallel rods having good light transmitting characteristics, such as Lucite, quartz or glass. Thecut and polished ends of the rods would form the inner and outer surfaces of the resultant faceplate. This particular arrangement has the shortcoming that it is extremely diicult to make, and, in addition, the material which holds the rods together is not vacuum tight under all conditions of use, handling, shock, and thermal change.

My faceplate utilizes an entirely diiferent concept, namely, the use of photosensitive glass. This glass which is commercially available from'the Corning Glass CQ. has the characteristic that when it is irradiated by ultraviolet light shining through a mask and then properly treated, the exposed and unexposed areas have `different characteristics. For example, one of these areas may be more readily etchable while the other is not, o1 one v of these areas may be transparent while the other acquires a color. A more complete discussion will be found in the article entitled Photosensitive Glass by Donald Stooky, which appeared in Industrial Engineering and Chemistry, April 1949, vol. 41, page 856.

AI form my faceplate for the cathode ray tube from `photosensitive glass of the type which turns dark. To

accomplish this', a sheet of suitable glass is irradiated with ultraviolet light through an opaque mask having a large number of transparent parallelV vertical lines, and a large number of` transparent parallel horizontal lines. Alternatively, a mask having a single set of parallel lines may be used by making a number of exposures, and rotating the mask between exposures. In accordance with my invention, the resultant faceplate when exposed and treated as above described, is subdivided -by a dark latticework into a myriad of small prism like elements having dark borders, which separate adjacent prisms.

It is apparent that the use of horizontal and vertical lines would produce a cube like arrangement, while the mask rotation would produce multifaceted prism like elements. When a faceplate made by the first method is viewed from the back or front, the faceplate is perfectly transparent. However, looking at the faceplate from any other angle is the same as trying to look through a'double set of Venetian blinds, one set being horizontal and the other being vertical. The faceplate produced by the second method would produce a similar visual effect. 'I'his novel faceplate is now incorporated into a cathode ray tube, and a fluorescent screen is deposited on its inner surface in the usual manner.

Fig. 2 illustrates, in fragmentary form, the structure of my light collimating faceplace. Now when a point of light is generated on the fluorescent screen, the light easily passes outwards through the clear portion. However, it is impossible for the light to diverge, due to the darkened Venetian blind like structure. When this novel faceplate is used in the apparatus of Fig. l, a spot of light can aifect only a minute area of recording material. In this way, divergence of the light is eliminated, resulting in collimated light which provides `a sharp recording on material 26.

Having disclosed the principles and one embodiment of my invention, I desire to be limited only by the following claims.

What is claimed is: v

l. Apparatus for recording the presentation on a cathode ray tube, comprising in combination a faceplate for said cathode ray tube, said faceplate comprising a sheet of transparent material subdivided into prism like elements having dark borders which separate adjacent prisms; a fluorescent screen on the inner surface of said faceplate, whereby a light pattern may be produced; a lilm of transparent conductive material; a coating of photoconductive material; means exposing said coating of photoconductive material to the light of said pattern; a conductive plate spaced from said coating; and a potential sensitive material positioned between said coating and said plate.

2. Apparatus for recording the presentation on a cathode ray tube, comprising in combination -a faceplatel for said cathode ray tube, said faceplate comprising a sheet of transparent material subdivided into prism like elements having dark borders which separate adjacent prisms; a fluorescent screen on the inner surface of said faceplate whereby a light pattern may be produced; a lilm of transparent conductive material; a coating of photoconductive material positioned in area contiguous relationship with said film whereby said coating of photoconductive material is exposed to the light from said pattern; a conductive plate spaced from said coating; and a potential sensitive material positioned between said coating and said plate.

3. Apparatus for recording the presentation on a cathode ray tube, comprising in combination a faceplate for said cathode ray tube, said faceplate comprising a sheet of transparent material subdivided into cube like elements having dark borders which separate adjacent cubes; a fluorescent screen ion the inner surface of said faceplate whereby a light pattern may be produced; a film of transparent conductive material positioned on the outer surface of said faceplate; a coating of photoconductive material positioned in area contiguous relationship with said lm whereby said coating of photoconductive material is exposed to the light of said pattern; a conductive plate spaced from said coating; a, potential sensitive material positioned between said coating and -said plate; and means to apply a potential between said film and said plate.

4. Apparatus for recording the presentation on a cathode Vray tube, comprising in combination a film of transparent conductive material; a coating of photoconductive material, positioned in area contiguous relationship with said film whereby said coating of photoconductive material is exposed to the light of said presentation; a conductive plate spaced from said coating; and a potential sensitive material positioned between said coating and said plate.

5. Apparatus for recording the presentation on a cathode ray tube, comprising in combination a film of transparent conductive material; a coating of photoconductive material; positioned in area contiguous relationship with said film whereby said coating of photoconductive material is exposed to the light of said presentation; a conductive plate spaced from said coating; a potential sensitive material positioned between said coating and said plate; and means to apply a potential between said film and said plate.

6. Apparatusfor recording the presentation on a cathode ray tube, comprising in combination a cathode ray tube having a light collimating faceplate; a fluorescent screen on the inner surface of said faceplate, whereby a light pattern may be produced; a lm of transparent conductive material; a coating of photoconductive material; means exposing said coating of photoconductive material to the light of said pattern; a conductive plate spaced from said coating; and a potential sensitive material positioned between said coating and said plate.

7. Apparatus for recording the presentation on acathode yray tube, comprising in combination a cathode ray tube having a light collimating faceplate; a fluorescent screen on the inner surface of said faceplate whereby a light pattern may be produced; a film of transparent conductive material; a coating of photoconductive material positioned in area contiguous relationship with said tilm whereby said coating of photoconductive material is exposed to the light from said pattern; a conductive plate spaced from said coating; and a potential sensitive material positioned between said coating and said plate.

8. Apparatus for recording the presentation on a cathode ray tube, comprising in combination a cathode ray tube having a light collirnating faceplate; a fluorescent screen on the innei` surface of said faceplate whereby a light pattern may be produced; a film of transparent conductive material positioned on the outer surface of said faceplate; a coating of photoconductive material positioned in area contiguous relationship with said film whereby said coating of photoconductive material is eX- posed to the light of said pattern; a conductive plate spaced from said coating; a potential sensitive material positioned between said coating and said plate; and means to apply a potential between said lm and said plate.

References Cited in the tile of this patent UNITED STATES PATENTS 1,858,361 Desirello May 17, 1932 1,940,882 Rich Dec. 26, 1933 2,248,758 Higonnet et al July 8, 1941 2,373,114 Goldsmith Apr. 10, 1945 2,732,469 Palmer Jan. 24, 1956 2,839,602 Fries .lune 17, 1958 

